Saturday 2 May 2009 19.01 EDT
First published on Saturday 2 May 2009 19.01 EDT

Opening Reif Larsen's The Selected Works of TS Spivet brings to mind that useful old instruction of Mark Twain: "Persons attempting to find a motive in this narrative will be prosecuted; persons attempting to find a moral in it will be banished; persons attempting to find a plot in it will be shot." Larsen wants to transport his reader to something like the world of Huck Finn, that place of adventure where adult codes are suspended. To this end, he places us in the head of Tecumseh Sparrow Spivet (TS for short), a 12-year-old prodigy with a compulsion to make maps of the world in order better to understand it.

Spivet lives on Coppertop Ranch in the wilds of Montana and it quickly becomes clear that the cartography he is interested in is not the stuff of the Ordnance Survey. His co-ordinates are all over the place: he maps the flight paths of bats around his house, the dynamics of his sister shucking corn cobs, the spread of McDonald's in northern Montana, the rising waters of the local lake, which he believes is set to inundate the town. Many of these maps illustrate the margins of his story, along with all sorts of other digressions and diagrams.

The result is a wilfully original and diverting book, full of carefully penned ephemera, a bit like Schott's Miscellany written as a confessional novel. In design, it appeals to the same contemporary nostalgia for the niceties of between-the-war text books and all things Baden-Powell. There is, of course, a reason for Spivet's mapping. The year before, we come slowly to learn, he was involved in an accident with a gun in the barn in which his beloved brother died (he didn't pull the trigger exactly, but his mind was certainly on higher things). The world had always seemed an indecipherable place to Spivet, but that event has made it infinitely more so. The mapping had seemed a hobby; now it appears to be a psychological necessity.

Spivet learnt the scientific method from his mother, an obsessive entomologist, and hides it from his father, a straightforward cowboy, who routinely uses "New Yorker" as a pejorative. With the help of a teacher, his maps have gained an improbable fame in leading scientific journals - when the novel opens, Spivet has just been awarded a grand prize by the Smithsonian Institute for his work. Believing him to be an adult, the institute has invited him to accept the award at a dinner in Washington. In order to attend, Spivet runs away from home, boards a freight train and sets off on a very personal voyage of discovery.

Much of this rambling quest takes place in his head. Spivet is that staple of contemporary literature from Salinger onwards: the misunderstood child genius, damaged, hypersensitive, refusing to grow up and precocious way beyond a fault. He is an alternative version of the narrator of The Curious Incident of the Dog in the Night-time, a product of our strange fetishisation of Asperger's, a child who uses lists and formulae as a defence against the messiness of the world. For Spivet, maps are what "forms bridges between here and there"; "I suppose children are particularly susceptible to such irrational connections," he suggests, in his professorial tones. "With so much unknown, they are less concerned with the sticky details than with trying to create a working map of the world."

The book that has grown out of that working map created a minor sensation when it was submitted to American publishers last year; Larsen, a graduate of the famed Columbia creative writing school, arrives with all the resultant hype. You can see exactly why it caused publishers to sit up. It is charming and kooky; it's like an attention-deficit Encyclopaedia Britannica, the kind of book adults believe children might like to read.

You can bet Larsen was an avid disciple of Dave Eggers's McSweeney's publishing project, which promoted writers in Eggers's own image - reinventing genres, fizzing with pop cultural references and heartfelt quirkiness. In some ways, this book might itself have been mapped to a McSweeney's blueprint; it is defiantly retro, it would resist digital formatting (though naturally there is an attendant website).

None of which makes it bad. But I did have two difficulties with it. The first, slightly unfair one, is that if you take away the brilliant typography and illustration, the story clunks, particularly toward the end. The second is that at no point did I feel that this was at any stretch the voice of a 12-year-old boy. Even the New Yorker's resident outlier Malcolm Gladwell wouldn't have sounded like this at 12: "Last year, I did an illustration for an article in Science magazine about a new technology at ATMs and automated kiosks that registered not just the tone of the customer's voice but also his or her facial expressions."

Much of the wit of the book arises from this disjunction, as in the moment when Spivet is faced with a rattlesnake and falls into an existential reverie: "Was there an acknowledgement - beneath the assigned roles of fear, predation, territoriality - of our shared sentience? A part of me wanted to reach out to the rattlesnake and shake his invisible hand." But it also courts a deadening kind of irritation. In one chapter, Spivet anatomises, rather riskily, the "five different kinds of boredom": from "anticipatory boredom" (where the looming presence of something in the near future prevents you from being able to concentrate on anything) to "let-down boredom" (where an event or activity is expected to be a certain way only for it to turn out differently).

By this point, I couldn't help feeling that he might have included a sixth type, what might be called "curiosity boredom": the kind that is allied to unstinting invention, an excess of precociousness.

One effect of reading this book was to have me go back and read a comparable debut, Nicholson Baker's The Mezzanine, which also revelled in marginalia and footnotes. There was a palpable difference between the two; whereas the obsessions of Baker's (adult) narrator - about wing-flap milk cartons, and moving staircases - seemed genuinely compulsive, and to have grown out of a lifetime of looking, Larsen's seem too often the kind of thing that you might expect a prodigy could become hooked on in this kind of book.

The author wants you to lose yourself in the thickets and dead ends that line the route of his spectacular-looking road trip; I enjoyed the scenery, but I never did get properly lost along the way.